Macintosh Monitor Sensing

[Numbering scheme] The Macintosh video port features a mechanism that enables sensing the type of monitor being attached to the video port. In New Technical Note HW 30 - Sense Lines, Apple explains the mechanism.
Below are drawings of all sensing possibilities. Shown are the connections needed between the three sense pins, of which the numbering scheme is given at the left.

Sensing Type 0 Sensing Type 1 Sensing Type 2 Sensing Type 4
[Image] [Image] [Image] [Image]
21" Color Monitor
1152 * 870
75.08 Hz 		15" Monochrome Monitor
640 * 870
75.08 Hz 		12" Color Monitor
512 * 384
60.15 Hz 		NTSC Monitor
640 * 480
59.94 Hz Interlaced


Sensing Type 3
[Image] [Image] [Image] [Image]
21" Monochrome Monitor
1152 * 870
75.08 Hz 		Unused Unused Unused


Sensing Type 5
[Image] [Image] [Image] [Image]
Unused Unused Unused 15" Color Monitor
640 * 870
75.08 Hz


Sensing Type 6
[Image] [Image] [Image] [Image]
Multiple Scan 14"
640 * 480
832 * 624 		Multiple Scan 16"
640 * 480
832 * 624
1024 * 768 		Multiple Scan 21"
640 * 480
832 * 624
1024 * 768
1152 * 870 		14" Color Monitor
640 * 480
66.67 Hz


Sensing Type 7
[Image] [Image] [Image] [Image]
PAL Encoder
768 * 576
50.00 Hz Interlaced 		Unused Unused Unused
[Image] [Image] [Image] [Image]
Unused Unused Unused NTSC Encoder
640 * 480
59.94 Hz
[Image] [Image] [Image] [Image]
VGA
640 * 480
59,94 Hz
SuperVGA
800 * 600
55.98 Hz 		Unused Unused Unused
[Image] [Image] [Image] [Image]
Unused Unused Unused 16" Color Monitor
832 * 624
74.55 Hz
[Image] [Image] [Image] [Image]
Unused PAL Monitor
768 * 576
50.00 Hz Interlaced 		Unused Unused
[Image] [Image] [Image] [Image]
Unused Unused Unused 19" Color Monitor
1024 * 768
74.93 Hz
[Image] [Image] [Image] [Image]
Unused Unused Unused Unused
[Image]
No Monitor

2002-05-02